connecting loop wire and feeder wires

Mike Regan has a video on Lionel.Com in the video tutorial section . It's called wiring 101.  

He explains no need to connect the retun end back to the transformer. Just the one end out from the transformer.

ralph

Assuming you're not running DCS or another digital system, connect the end of the loop back to the transformer.  This will enhance electrical distribution and reduce voltage loss at the loco.  At the end of a 100' length of wire, there will be substantial voltage drop otherwise. 

Connecting both ends reduces the voltage drop to half at the midpoint of the wire loop, and even better for all the wire after the midpoint.

I just watched the Lionel video on wiring with a bus.  VERY disappointing!!  Mike implies that you could have bus wires up to a mile long and you would still only need to use 16 Gauge wire!!  He also does not mention that the common/ground leg of a bus system for 4 loops will carry 4 times as much current as for a single loop.

PLEASE do not believe this video!!

Optimally the transformer sits in the middle of the U. Wires go each way to the end, no return needed.

If the track actually loops around you can run the main power down the middle and run drops off both sides to your track.

OR

If you have a complete circle bent in a U, you can make the Main power follow under the track around the loop and in that case I'd agree with RJR. Hook up both ends.

As Ralph points out, this works well for conventional.

Do not loop it back if you ever plan on adding DCS.

If you are considering DCS Go to the MTH website and buy Barry's Book the DCS Companion. Follow the wiring guide in that, it will work for running TMCC, Legacy , DCS and Conventional. Best of all worlds, but it uses a lot more wire.

This method of wiring also happens to make finding a shorted section of track a lot easier in the future.

This is a point to consider.

The thing I didn't consider is that the track itself will act as a jumper across the gap at the end IF the track is a complete loop without any block insulators in the open gap.  It is better to use copper wire as the "jumper", rather than relying on steel track.

For the layout as shown in the video - 8' x 16' - the total run of bus wire is about 100' out and back.  A 16 gauge wire has a resistance of .4 ohms per 100 feet.  For Mike's comment that 16 gauge wire would still work for 800' x 1600', that would be 40 ohms of resistance, far too much.  Any drop of as little as 1 ohm will show up as slowing of PW conventional locomotives.  Fortunately, modern cruise-control engines aren't as sensitive to voltage drops.

Dale,

   You are correct sir.

PCRR/Dave

"Any drop of as little as 1 ohm will show up as slowing of PW conventional locomotives."

You overly generous.  A 0.25 ohm resistance will reduce voltage at 5 amps. by 1.25 assuming all connections are perfect.  I have a DCS layout which, based on my 70 years experience with layouts, is wired with 12-gauge common ground that carries all common power for the layout.  It loops around layout and each end is connected to the transformers.  It's probably handing 15-20 amps when everything is going full blast.

I also use 14-gauge for the hot feeds, and recommend nothing less.  Dale, if the video says what you say it is, it's worse than useless. 

You got it.

For conventional, current can flow both ways in the loop out from the transformer to the engine, this effectively cuts wire resistance in half at the farthest point.

Less resistance means more volts get to the engine.

I suspect the reason your 4-6-0 ran better is the current draw for the smoke. Those MTH smoke units eat lots of power. Lots of power flowing in a wire means lots of voltage drop in the wire. Flowing power from both ends means less lost in the wire and more for the engine.

Russell, Thank you for your service, I served 4 years in the Air Force from 1977 to 1981 at Malstrom AFB in Montana.

 And thank you to everyone for all your knowledge and help on this site. Have a great weekend

Dale you read my mind. I have been debating this in my mind. See if I have this right. If I run two identical power districts each with its own transformer,feeds and ground wires,  I will get less voltage drop than having one ground wire for BOTH district.  Did I get that right or did I screw it up?

Having two common/ground wires will cut the voltage drop on the common/ground leg.

If the common wires run next to each other, you would reduce the common resistance when you are operating either or both power districts if you tie the wires together at both ends and a few spots in between, essentially doubling the copper available at all times.

Not trying to be dumb here but does that translate to less voltage drop at the track? 

Yes.

Effectively, you then have a Common return wire-run for each power district--a return for each separate Hot conductor.

As described on my layout above, I try to accomplish the same job with a 20 amp single Common solid copper return conductor[#12 ga,] covering both 10 amp districts--not as capable as Dale M describes but enough for my light load trains.

This forum is so nice. Complete strangers always willing to help!  Thanks to all you forumites who answer endless dumb questions from guys like me

I don't recall any dumb questions,

Me either!

I just use 1 common buss for the entire layout using Romex house wire. If not using DCS this is feasible.

Described here

www.jcstudiosinc.com/BlogShowT...=432&categoryId=

Dale H

I use common ground buss with DCS.

Back to the OP post. By looping the wire aka connecting at both ends one effectively doubles the size of the wire. Doubling the size of the wire gives you less voltage drop. This is because the current has 2 paths to flow.

What you use depends on cost and what is available to you. Doubling the size of the wire generally costs less than double the price. Therefore, it would be less expensive than using twice as much wire to get the same result. If you have a lot of the smaller gauge stuff use it as it better than sitting in a drawer somewhere while you go out and buy bigger stuff.

A power outage kept me from an earlier response

842:

This turned out to be a post with more info than I expect that you hoped to get.  I APOLOGIZE for leading you astray in my initial response. But all's well that ends well.

Dale M: thanks as usual for keeping us straight

Gentlemen,

   Great thread, very educational.

PCRR/Dave

Also , very useful for me since I'm doing a lot wiring now.

Larry